High-frequency receiving system



A ril 15,1930. H.E .A1LLEN 1,155,091

HIGH FREQUENCYREGEIVING SYSTEM Filed Maroh -'29, 1929 Inventor I HumiAuen,

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Patented Apr. 15, 1930 UNITED STATES PATENT oFFicE' HUGH E. ALLEN, OFSCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEGTRIC COMPANY, ACORPORATION OF NEW YORK HIGH-FREQUENCY RECEIVING SYSTEM Applicationfiled March 29, 1929. Serial No. 351,093.

My invention relates to high frequency receiving systems for use inconnection with remote control systems such, for example, as thatdisclosed in my application, Serial No.

195,388, filed May 31, 1927, and entitled Ra mote control system ofwhich my present application is a continuation in part.

It has for one of its objects to provide a receiving system employing anelectron discharge device the electrodes of which may be energized froman alternating current source, which is more economical to constructthan known circuits utilizing alternating energizing currents and whichpossesses the characteristic of sensitiveness to received high frequencyimpulses.

The novel features which I believe to be characteristic of myinventionare set forth with particularity in the appended claims.

My invention itself, however, both as to its organization and method ofoperation, to gether with further objects and advantages thereof, maybest be understod by reference to the following description taken inconnection with the accompanying drawing in which Fig. 1 represents anembodiment of my invention, and Fig. 2 represents a modificationthereof.

Referring to the drawing I have represent- P ed at 1 an electrondischarge device having an anode, a cathode and a grid. This dischargedevice is arranged to be energized by alter nating currents, which maybe of commercial frequency as, for example, sixty cycles per second, andwhich are supplied thereto by means of a transformer 5 having aplurality of secondary windings 6, 7 and 8. Potential is supplied to thegrid of the discharge device by means of the winding 6 and tothe anodethereof by means of the winding 8, whereas the cathode is energized fromthe winding 7 The adjacent terminals of the windings 6 and 8 areconnected to the cathode, and the potentials on opposite terminals ofthese windings, which are displaced in phase by 180, are supplied to thegrid and anode. The outer terminal of the winding 8 is connected to theanode through relay 9 and the outer terminal of winding 6 is connectedto the grid through a resistor 10 and secondary winding of an inputtransformer 11.

The primary winding of tranformer 11 may, of course, be connectedthrough a suitable coupling means to a power transmission line overwhich high frequency carrier currents are transmitted, or to an antenna,or other means whereby high frequency currents, for control of remoteequipment, etc., are supplied to the discharge device.

In the operation of the device, as thus described, it will be apparentthat the winding 6 supplies a bias potential to the grid of device 1during the half cycle when the anode is positive. Thus during this halfcycle the device operates as a biased detector. The anode current,during this half cycle, assuming that no high frequency electromotiveforce is supplied to the grid, is maintained at a suitably small value,or a zero, by means of the grid potential. hen high frequencyelectromotive force is impressed upon the grid, the negative gridpotential will be sufficiently opposed by the positive half cycles ofthe high frequency wave to permit sufficient anode current to fiow inthe device to cause operation of relay 9. p

The condenser 12, which is connected in arallel with the winding ofrelay 9, becomes charged by the anode current when the anode is positiveand discharges its current through the winding of relay 9 when the anodeis negative. the relay is maintained during the negative half cycle andthe relay is thereby prevented from chattering.

The input circuit to the discharge device may, of course, be tuned tothe frequency of the high frequency electromotive force, in any suitablemanner, as by connecting a condenser across the secondary winding oftransformer 11 or, if desired, the transformer may be one havingsuflicient distributed capacity to render it inherently resonant at thefrequency at which the system is to operate.

To obtain maximum efficiency of the device, it is necessary that the 180phase relation which exists between the potentials at the outerterminals of windings 6 and 8 be preserved upon the grid and anode ofthe dis- In this way the energization of charge device during periodswhen no high frequency electromotive force is impressed upon the gridand that, as will be explained hereinafter, the grid should becomenegative substantially simultaneously with the anode becoming positive.If any appreciable current be permitted to flow in the grid circuit,this current flowing in the impedance of thatcircuit will cause adeviation from the above relation between the potentials impressed uponthe grid and anode of the device and a consequent diminution inefficiency and sensitiveness of the device.

Theanode current, of course, except as indicated hereinafter, may bemaintained at zero, or at a suitably small value, by means of the biaspotential on the grid. During the half cycle, when the grid is positive,however, current will flow in the grid circuit. This current will causeenergy to be stored in the inductance of the transformer 11 which energywill, in turn, tend to cause the grid to remain positive after the anodehas become positive. Consequently a short rush of current in the anodecircuit will occur at the beginning of each operative half cycle of thedevice independently of received high frequency electromotive force.This current will cause the condenser 12 to be charged during the firstposition of the half cycle when the anode is positive. This condenser,in turn, will discharge through the winding of relay 9 after the shortimpulse has passed. Thus the result of this flow of current is tonecessitate an adjustment of the relay 9 such that it will not respondto this current, which adjustment, in turn, causes a less sensitiveoperation of the relay to current flowing in the anode circuit inresponse to high frequency electro-motive force upon the grid.

To obviate this adjustment and to preserve the 180 phase relationbetween the grid and anode potentials the resistance 10 is inserted inthe grid circuit of such value that substantially no grid current flowsduring the half cycle when the grid is positive. The anode current maythen be maintained at Zero value or at a Very small value by means ofthe grid bias potential with the result that maximum efficiency of thedevice is obtained.

Fig. 2 represents a modification of the system shown in Fig. 1 in that atransformer 13 is employed for supplying energy of the frequency of theenergizing currents from the anode circuit of the device 1 to the gridcircuit thereof during the half cycle when the anode is positive. Thatis, when high frequency current is applied to the grid of the dischargedevice the current flowing in the anode circuit thereof will cause apotential impulse to be produced in the secondary winding of thetransformer 13 having the frequency of the power source. The secondarywinding of this transformer is connected in the rid circuit of thedischarge device in opposed relation to the winding 6 thereby tending tocause the grid of the discharge device to become positive during thehalf cycle when. the anode is positive.

It will thus be seen that when no high frequency current is received thebias on the grid of the discnarge device 1 during the l alf cycle whenthe anode is positive will be determined practically entirely by thepotential of the winding 6. Then carrier is received, however, andcurrent is caused to flow in the anode circuit during the half cyclewhen the anode is positive the negative bias potential upon the gridwill be reduced by'the amount of the instantaneous secondary voltage ofthe transformer 13. This potential may be sui'iicient to drive the gridpositive. In this way the current flowing in the anode circuit and hencethe sensitivity of the device may be greatly increased.

The resistance 10 will of course serve to so reduce the grid currentthat the relation indicated above between the potentials on the grid andanode is obtained during the period when no carrier is received.

The sensitivity of the device may be fur ther increased by tuning thefeedback circuit to resonance at the frequency of the power source. Thismay be effected by connecting a condenser 14 of proper capacitanceacross the primary winding of the transformer 13.

lVhile I have illustrated my invention in connection with a receivingsystem having a particular type of input and output circuit, it will ofcourse be apparent that I do not wish to be limited thereto since myinvention has utility in connection with systems employing other formsof input coupling means and load circuits as well.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a receiver for high frequency electric impulses employing anelectron discharge device having an anode, a cathode and a grid, asource of alternating current, connections from a neutral point on saidsource to said cathode and from opposite points on said source to saidgrid and to said anode such that voltages on said grid and on said anodeare in opposed phase relation, means for impressing high frequencyimpulses on said grid, means in said grid connection for correcting fordisplacement in phase relation between said grid and anode voltagesresulting from said last means and current responsive means associatedwith said anode.

2. In a receiver for high frequency electric impulses employing anelectron discharge .device having an anode, a cathode and a grid,

a source of alternating current, connections from a neutral point onsaid source to said cathode and from opposite points on said source tosaid grid and to said anode such that voltages on said grid and on saidanode are in opposed phase relation, means for impressing high frequencysignaling impulses on said grid, means in said grid connection forreducing the current flowing therein substantially to zero during thehalf cycle when the grid is positive with respect to the cathode, andcurrent responsive means associated with said anode.

3. The combination, in a high frequency receiver of an electrondischarge device having an anode, a cathode and a grid, a source ofalternating current, connections from a neutral point on said source tosaid cathode and from opposite points on said source to said gridandanode, input means having energy storage capacity connected between saidgrid and cathode, and means for preventing storage or energy in saidmeans during the half cycle when the anode is negative thereby toprevent the fiow of anode current due to potential on the grid resultingfrom energy stored insaid means.

4. The combination, in a high frequency receiver, of an electrondischarge device having an anode, a cathode, and a grid, a source ofalternating electromotive force, connections from a neutral point onsaid source to said cathode and from opposite points on said source tosaid grid and anode, a relay connected in series between said anode andcathode, an input transformer having a secondary winding connectedbetween said grid and cathode and a resistance connected in series withsaid winding to prevent flow of current in said relay resulting fromenergy stored in said means when no high frequency electromotive forceis supplied to the grid.

In witness whereof, I have hereunto set my hand this 28th day of March,1929.

HUGH E. ALLEN.

